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Re: Graphics issues

From: Andreas Schik
Subject: Re: Graphics issues
Date: Tue, 30 Aug 2011 11:38:18 +0200
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Hello Eric,
thanks forlooking inthose issues.

Am 30.08.2011 05:17, schrieb Eric Wasylishen:
> Hi Andreas,
> On 2011-08-29, at 5:08 AM, Andreas Schik wrote:
>> Hi there,
>> on the weekend, I update GNustep from SVN (trunk) and did a completely
>> fresh installation. Since then, I have several graphics issues.
>> 1. When using gnustep-art, GWorkspace does not display file icons. I am
>> using a viewer in symbol mode. While the navigation control in the upper
>> part displayes correctly, no file/directory icons are shown in the lower
>> part (symbol view). This does not apply to to gnustep-cairo. Here, the
>> correct file type icons are displayed.
> This is fixed now. I made a mistake when modifying NSCachedImageRep last week 
> (deleted the -draw method when I shouldn't have).
OK, I'll try asap.

>> 2. With both backends, it seems that images which do not have a
>> resolution of 72x72 dpi are not displayed correctly. Details:
> As far as I know, the current behaviour is correct and matches what Cocoa 
> does.. [snip]
I would not doubt that this behaviour is correct. I just saw that it was
different than before my update.

>> - 72x72 is of course a value that applies to the very notebook I am
>> using. Don't know whether this applies to other machines as well.
> The GNUstep gui is rendered at 72x72dpi by default, so it applies to all 
> machines, [snip]
Does this mean, that images are always supposed to have 72x72 dpi,
otherwise they will be scaled one way or the other?

> The only exception is on Windows, where if you increase the system DPI in the 
> Windows control panel, GNUstep will respect that. It does that by computing a 
> scale factor, so 96 DPI in windows (the default) = 72 DPI in GNUstep.
>> - Images are scaled in strange ways. I observed 75x75 dpi images to be
>> upscaled in the Y direction only.
> Hm, that shouldn't happen.
At least, that was what my bare eye told me. The flower seemed stretched
into the Y direction only.
BTW, the physical resolution of my screen is 75x72 and to me it seems
that the EtoileLoge is transferred pixel-wise to the screen. This would
again explain why it is enlarged in the Y direction, but in the X direction.
But on the other hand, you say that the physical relution should be
ignored by GNUstep. How do the -compositeToPoint: methods work?

>> There were also images with 90x90 dpi
>> being downscaled.
> I think that's expected. e.g. a 90x90 pixel image with a DPI of 90x90 would 
> have a size of 1x1 inch or 72x72 points, and if the GUI is at the default DPI 
> of 72, that maps to 72x72 pixels (so in other words the image is downscaled.)
>> - Example is Etoile's MenuServer. While the middle part displays
>> correctly, the left and right edges as well as the logo are distorted.
>> The middle image is 72x72 dpi the others are 75x75 dpi.
> I wasn't able to get MenuServer to work, but I tried drawing the 
> EtoileLogo.tiff image in GSTest and it appeared correctly (a bit blurry and 
> scaled up because of being 75dpi). So I'm not sure what is going wrong here.
What bothers me is that noth images have more dpi than GNUstep/my
screen, but the one (EtoileLogo) seems upscaled while other seems
downscaled. I have the impression that in the case of Etoile, the image
is simply transferred pixel

>> 3. gnustep-cairo does not handle themes very well. Neos, at least has
>> some glitches, e.g. missong knobs on scrollbars. Not a major problem,
>> though.
> A few images in the Neos theme just need to be set to 72dpi. The scroller 
> knobs are actually being drawn, but they're really hard to see because they 
> are 96dpi and being downscaled.
I see.

> Sorry about the trouble created by having images with a DPI != 72 being 
> scaled. It's inconvenient but I think it's correct in the long run.
Well, it might be correct, but it confused me anyway :-) I was thinking
that images for screen elements were transferred pixel-wise, ignorig the
DPI. In that case they would need more or less screen estate, but would
not up or down scale.
Anyway, thanks for the xplanation.

Ah, btw, does GNustep support SVG images?


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